Scientists have discovered that a detectible increase in the blood content of superficial mucous membrane occurs proximate cancerous and precancerous lesions in the colon relative to the blood content of healthy tissue as described in, for example, R K Wali, H K Roy, Y L Kim, Y Liu, J L Koetsier, D P Kunte, M J Goldberg, V Turzhitsky and V Backman, Increased Microvascular Blood Content is an Early Event in Colon Carcinogenesis, Gut Vol. 54, pp 654-660 (2005), which is incorporated by reference herein. This phenomenon is referred to as early increase in blood supply (EIBS).
Relying on this phenomenon, it is known that it is possible to predict an area of potential abnormality based on early increase in blood supply (EIBS) in the area of abnormality. Further, it has been discovered, that by using a probe applying collimated light to an area of interest, and detecting the amount of absorbed and reflected light it is possible to provide blood content or blood flow information to a clinician to guide an endoscope to detect a possible abnormality in vivo without an invasive procedure. Such techniques have been described for example in U.S. patent application Ser. No. 11/937,133 filed on Nov. 8, 2007, issued as U.S. Pat. No. 8,162,828 entitled “Blood Content Detecting Capsule”, assigned to the assignee of the present invention, which is incorporated by reference herein.
Typically, blood content or blood flow detection relies on measuring the amount of light reflected from the tissue mucosa back into the blood content sensor. Because systems rely on measuring the amount of reflected light, the accuracy of the measurements are greatly impacted if the blood detection apparatuses window is obstructed by foreign liquid or solid matter on the lens. Further, the accuracies of any measurement or foreign matter detection techniques are impacted if there is extraneous light detected by the sensors as a result of other observation devices such as a traditional CCD camera light.
Various techniques exist for removing foreign liquid or solid matter from endoscope lenses while in vivo, e.g., nozzle sprayers of water onto the endoscope or blood content sensor windows, however, techniques still lack a method to detect if the observation window is actually clean. In an observation only system, i.e., one without a blood content sensor, an operator may determine if there is foreign matter on the observation window by subjectively viewing of the image. However, in blood content sensor systems, there is no viable image for an operator to view, therefore an operator cannot make a determination about the presence of foreign matter on the detector window.
Further, when it is desirous to determine the presence of foreign matter on the blood content sensor window, the endoscope tip or blood content sensor window is removed from the surface of the tissue. As a result, illumination light from the scope observation source, e.g., endoscope camera, may be scattered by the surface of the living tissue and reach the receiving fibers of the blood content sensor. In that case, a false reading of the level of foreign matter present will occur because light from the observation source is attributed to the blood content sensor itself, thereby falsely determining the presence or absence of foreign matter.
Accordingly, in order to improve the accuracy of blood content measurements there needs to exist a technique for objectively determining if the measurement lens is obstructed by foreign matter.